Second step: Edit Library/Preferences/SystemConfiguration/com.apple.Boot.plist file.
To do this first copy com.apple.Boot.plist to your desktop (now you are able to edit the file), open it with text editor and than add this string.

<key>GraphicsEnabler</key>
<string>Yes</string>

Save file and copy it from desktop back to Library/Preferences/SystemConfiguration/ and replace the old plist file.

This method will work on many cards, third step is only for ATI x1800 card.

Third step: Copy ATI1900Controller.kext and ATIRadeonX1000.kext you downloaded earlier to System/Library/Extensions and replace the old files if exist.
Run Kext utility to fix permissions and reboot, if kernel panic, reboot and try again ( if not working ).
Now your card should be fully functional, QE/CI Enabled, with high resolution…